Drain hole drilling equipment



Dec. 13, 1955 J. s, MQCUNE ETAL 2,726,847

DRAIN HOLE DRILLING EQUIPMENT Filed March 31, 1952 2 Sheets-Sheet l ITO/4N 5. Ma Z/NE,

WLL/AM E. HAN/(5,

INVENTORS.

A 7' TOENEY.

Dec. 13, 1955 5 cc ET AL 2,726,847

DRAIN HOLE DRILLING EQUIPMENT Filed March 31, 1952 2 Sheets-Sheet 2 rioH/v 5. Mc UNE, MAL/AM E. HAM/K5, INVENTORS.

ATTORNEY.

.the main bore of the well.

United States Patent 0 DRAIN HOLE DRILLING EQUIPMENT John S. McCune and William E. Hanks, Long Beach, Calif., assignors t0 Oilwell Drain Hole Drilling Co., Long Beach, Calif., a corporation of California Application March 31, 1952, Serial No. 279,554

13 Claims. (Cl. 2551.6)

This invention relates to improved methods and apparatus for drilling and protecting oil well drain holes.

In order to increase the production of an oil well, it is sometimes desirable to drill, in addition to the main hole of the well, one or more drain holes extending laterally from the main bore into the producing formation. These drain holes facilitate the flow of fluid into the well by providing open paths leading into the main bore from what would otherwise be relatively remote portions of the producing formation. in the past, however, the salutary effect of such drain holes has generally lessened or been lost completely after the well has been in production for a period of time, by reason of the tendency of the drain hole walls to collapse and close the hole against further fluid passage.

The general object of the present invention is to provide improved methods and apparatus for protecting drain holes against such collapse, to thus assure their maintenance in an open condition for readily passing fluids into the main well bore. Briefly, this result is achieved by a unique method of positioning within a laterally extending drain hole a tubular structure adapted to positively support the wall of the hole and prevent its collapse. More specifically, I first lower into the well a vertically elongated unit having a lower longitudinally flexible tubular section, next advance that lower section, as permitted by its longitudinal flexibility, laterally from the main bore into a laterally extending drain hole, and then disconnect the upper section of the unit and remove it separately from the well, leaving the lower section in the drain hole to support its wall. For most elfective support of the wall, the lower section of the device is transversely rigid, though having the above discussed longitudinal flexibility, and for this reason may comprise a number .of articulately or movably interconnected rigid tubular segments.

:For permitting disconnection of the two sections of the device within a well, the sections are interconnected by a joint which is preformed to be broken by force exerted against the upper section of the device. This joint preferably comprises a loose threaded connection or a pin and slot connection adapted to be broken by rotation of the upper section of the device. In order that the lower section may aflord support to the entire extent of the drain hole wall, the joint is desirably broken when located at substantially the juncture between the drain hole and To permit lateral deflection of the joint itself to a location just within the drain hole,

the upper section of the device may have a longitudinally flexible portion, typically of essentially the same segmental construction as the lower section.

Particularly contemplated by the invention is the use, as a wall supporting structure, of a flexible tubular drilling shaft or collar, which is first employed for drilling the drain hole, and is then partially left in the hole for supporting its wall. The lower drill bit carrying portion of this shaft may be disconnectable from the upper portion of the shaft and the supporting drilling string by rotation Figs. 2 and 4, of a further variational 2,726,847 Patented Dec. 13, 1955 ice in a counterclockwise direction, i. e. by rotation in a direction the reverse of that normally used in drilling.

For introducing circulation fluid into the well, I may provide within the drill shaft or other tubular structure and leading to its lower end, a flexible fluid circulation hose. Preferably, this hose is releasably connected at its lower end to the apparatus, so that the hose may be disconnected and withdrawn from the well with the upper section of the device, leaving the lower section alone in the hole.

When the tubular unit is not a drill shaft, but instead is inserted into a drain hole as a liner after the drilling operation, the problem arises as to how to cause the unit to initially enter the lateral drain hole as it is lowered into the main bore. In certain instances, this is achieved by leaving the drilling whipstock in the hole, and using it to deflect the later inserted unit in the same manner that the drill shaft had previously been deflected. In other instances, however, it is desirable to cause the liner unit to enter the drain hole after removal of the whipstock. For this purpose, I contemplate providing in the tubular structure a spring which acts to yieldingly laterally deflect a lower end of the structure outwardly against the bore wall or casing, so that as the structure is moved downwardly within a well, its end searches for and ultimately enters the drain hole opening in the bore wall. This spring may comprise an elongated and longitudinally tensioned coil spring having its opposite ends connected to the tubular structure at axially spaced locations so that the spring tends to longitudinally bow the structure.

The above and other features and objects of the present invention will be better tmderstood from the following detailed description of the typical embodiments illustrated in the accompanying drawings, in which:

Fig. 1 is a side view partly in section of a drain hole drilling apparatus embodying the invention and shown positioned within a well;

Fig. 2 is an enlarged fragmentary side view of the Fig. 1 apparatus shown after disconnection of the upper section of the drill shaft from its lower section;

Fig. 3 is a further enlarged fragmentary sectional view of the lower portion of the Figs. 1 and 2 drill shaft;

Fig. 4 is a fragmentary view, corresponding to Fig. 2, of a variational form of the invention, comprising a tubular structure to be lowered into the well and drain hole after the drain hole has been drilled;

Fig. 5. is an enlarged fragmentary side view of the lower section of the Fig. 4 structure;

Fig. 6 is a fragmentary side view, corresponding to form of the in vention;

Fig. 7 is an enlarged fragmentary section taken on line N Fig. 8 is a fragmentary side view, partly in section, .of the lower section of a final form of the invention.

Describing first the form of the invention illustrated in Figs. 1 to 3, the apparatus is shown positioned within a well having a vertically extending main bore 10. The apparatus includes a flexible drain hole drilling shaft or collar 11, a rotary drilling bit 12 carried at the lower end of shaft 11, a rigid sectionally formed tubular drill string 20 supporting the flexible shaft within the well, and a whipstock body 13 for deflecting the shaft laterally from the main bore to form a laterally extending drain hole 14.

The whipstock body is of essentially conventional construction, having a lower anchor end 15 for engaging the bottom 16 of the main bore of the well to support the whipstock body therein. The whipstock presents the usual inclined or angular face 17, which is engaged by bit 12 and deflects it laterally to form the desired angular drain hole 14. At a side opposite'bit de- 7 eratio fleeting face 17, the whipstock body contains a side opening .orwindow' 18 through which the bit and shaft may advance laterally into the formation. Above bit deflecting face 17 and window 18, the'whipstoek body has an upper tubular portion 19 which acts as a sheath maintaining the contained portion of the flexible drill shaft in straight condition during a drilling operation.

The drill string or tool string '20 is in conventional manner formed of a number of stands of pipe'connected in an end-to-end series by threaded joints at 21. The lowermost pipe stand is connected at its lower end to .the upper end of the flexible drill shaft or collar 11 by a thread edjoint at 22. I

hej e lr d il 's a r so l llinclud a pa of upp .a d l wer seetions 23 and 24 interconnected by a releasbacloofi joint at 2 5. The lower section 24 of the his shaft carries at its lower end the rotary drilling h t ,2; d ma rt i a lybc o a a l i meter than upper section 23. Both of the sections are preferably fe a-" i d t a e r n e i dity, Wh e ei g l ngit inally llexible to permit deflection of the shaft along a curved laterally extending path as shown. To permit wn to form the interfitting lobes and recesses. (See ogrcppending application Serial Number 279,557, filed oneven date herewith, .now Patent No. 2,712,436.)

The connection 25 between the two sections of the drill or collar is so designed as to be releasable by force stee a ns dr l st in 2 While the pp ra is p sitioned within a well.

he hrolgen or diseonnected by left-hand or counterclockwise rotation Qf the dril'lingstring and upper sectipn of the flexible shaft after completion of a'drilling 1 lder that rotation of thedrilling string at the'surfaee of the earth will thus break'the threaded nection atZS, that i onnection is of a considerably looser and more easily broken construction than the 7 other threaded connections 21 and 22 of the drill string an i shaft, For this purpose, the threaded connection 25 may have fewer and more coarse threads than the joints s eazes ppl in clrculaapn fluid to drill bit12, the flexible shaft 11 may contain a flexible fluid supply hose 29. .B F .PLY2 the hose -29 is pe anen y n i a its upper end to the uppermost segment of upper seetion 23,

as at 1415, and is releasably connected at its lower end to bit 12 as by ar s'li cling telescopic connection 30. te se connection may include a tubular, end fitting ecting from thelower end of the hose and received within a tubular fitting fiz leading to the bit. A pair of seal rings 33 may 0 31 a fluid tight seal between member 31 and '32, while permitting relatively free upward withd wal of the hose carried member 31 from the bit earried member 32 when desired.

in placing the apparatus of Figs, 1 to 3 in use, whipstoel; bogly 13 is lowered into the main bore '16 of the well, and the flexible drill shaft 11 is then simultaneously advanced downwardly and rotated .in a right-hand direction, to be deflected by whipstock face 17 and drill a laterally extending drain hole 14. After ahole 05 a desired H e d, the drill string 20 and the assoupper section of the flexible drill shaft are then otated in a reverse or counter-clockwise direction, to d sconnect the shaft sections at 25,'f01lowing whichthe This connection may typically be a relatively loose right-hand threaded joint, which forming a passage through which fluid entering the bit may drill string and upper section of the shaft are removed from the well, leaving the lower section 24 of the shaft within the drain hole to support its wall. As the upper section is pulled upwardly it' carries with it the circulation hose 29, the initial upward movement of the hose serving to remove the lower hose carried discharge tube 31 from within bit carried tube 32.

In order that the wall of drain'hole 14 may be supported along its entire extent, the drain hole 14 drilled by bit 12 is preferably of a length corresponding substantially to the length or" lower section 24 of the flexible drill shaft. In the final condition of the drill shaft, back-off joint 25 is desirably located at approximately the juncture between main bore 16 of the well andthe drain hole. To avoid obstruction of the main bore by the lower section 24 of the shaft, the lower section should terminate just inside of the drain hole anddirectly adjacent the main bore as shown.

After all of the apparatus but lower section 24 of flexible drill shaft have been withdrawn from the well, the well is placed in'production, with the drill shaft section flow into the main bore of the Well. Since the segments 27 of the drill shaft-arerigid, they afford positive support to the wall of the'drain hole, to maintain the drain hol passage open to fluid flow. 1

Figs. 4 and 5 illustrate a variational form of the invention, which is structurally very similar to the flexible drill shaft or collar of Figs. 1 to 3, but does not itself serve to drill the drain hole into which it is positioned. Briefly, this second form of the invention comprises a tubular structure 11a including two longitudinally flexible sections 23a and 24a corresponding essentially to drill shaft sections 23 and 24 of Fig. 1. These two sections of the tubular structure are interconnected by a threaded back-oi joint 25a of the same structure as joint 25 in Fig; l. The

walls of segments 27a of the lower section contain a number of perforations 40, through which fluid from the for rnation may flow into the device for passage into the well. Instead of carrying a drilling bit, lower section 241; carries at its lower end a tubular bottom fitting 12a, having a blunt nose 34 containing openings 35 through which circulation fluid from hose 29a flows into the hole during lowering to clean out the hole in advance of the tool. Nose 34 carries a number of circularly spaced radial blades 36, which may taper to curved ends at 37, and which dig into the formation to retain section 24a against rotation in the drain hole. i

In using the Figs. 4 and 5 device, the tubular strueture 11a is lowered at the lower end of a tubular tool string. (not shown) into a well having a preformed lateral drain hole 14a. The flexible tubular structure is defleeted into the drain hole in some manner, as by a whipstoclg'such as is shown in Fig. l, and is advanced to the condi of the hole. Counter-clockwise rotation of the tub a; structure and upper section 23a of the shat'tthen 'bre the connection at 25a, so that the string and upper sect on may be withdrawn from the well. At'the same time, circulationhose 29a is withdrawn from the tubular struet ire As in Fig.1, the lower section 24a of the apparatus is preferably of such a length as to extend along the entire length of drain hole 14a, and to terminate just inside the drain hole and directly adjacent the main bore. When the .well is placed in production, the tubular section 24d serves to support the wall of the drain hole'agains't collapse, and tothus maintain the drain hole open to l1 "d h l flu d t s "s c on 2 q 'h e' r me t the al Qt ts meilt and n fl ws 21 the et ng int th r in 611 h tsn ention hish F nd. 7 shew a hird term. P? e is essentially the same as that shown in Figs. 1 to 3, ex-

on of Fig. 4 in which blades 36 dig into the formation girlie brie cept that the releasable back-off connection b is of a pin and slot rather than threaded construction. The upper section 23b of the Fig. 6 device has a depending element 41 receivable within an upper portion of an upper segment 42 of the lower section 2417. Element 41 carries one or more outwardly projecting pins 43, which are receivable within J-slots 44 in segment 42 of the lower section to releasably interconnect the two sections. This pin and slot connection is releasable by first moving the upper section slightly downwardly, then rotating it in a counterclockwise direction, and finally pulling it upwardly to remove the pins from slots 44. It will of course be understood that the diameters of the upper and lower sections 23b and 24b of the device may have any desired relation. In Figs. 6 and 7, these sections are typically shown as of the same diameter.

Fig. 8 shows a final form of tubular structure embodying the invention, which is constructed the same as the Figs. 4 and 5 device, except as to certain features which tend to maintain the lower end of the device in a laterally deflected condition for assuring its entrance into a lateral drain hole. For this purpose, I provide within the lower end of the lower section 24c of the device a spring 130, which may be received within a lower circulation hose 29c, and acts to longitudinally bow the lower portion of the device, as to the broken line position of Fig. 8. Hose 290 is received at its opposite ends within retaining fittings 131, which are attached to annular positioning elements 132, which in turn bear against shoulders 133 formed in two of the segments or members of section 240. Preferably, the shoulder against which the lower positioning element 132 bears is formed in the bottom hose fitting 12c of the device, while the shoulder against which the upper positioning element bears is formed in a different segment which is near but above the bottom hose fitting. Spring 139 is an elongated coil spring extending axially within hose 29c, and maintained in longitudinally tensioned condition by connection at its opposite ends to a pair of hooked elongated anchor elements 34. These anchor elements carry at their ends individual nuts which bear against web members 36, which are in engagement with the positioning elements 32 associated with the hose retaining fittings 31.

The tension of spring 30 is such as to normally tend to longitudinally bow the lower portion of the flexible tubular structure 24c and thus deflect it laterally, as to the broken-line position of Fig. 8, and against the bore wall of a well into which the device is lowered. In order that the spring may have such a bowing effect, the lower segments of the device are specially formed in a manner tending to return to a bowed condition. As in the other forms of the invention, these segments are formed by cutting a single pipe with a torch along axially spaced curved lines, such as to form interfitting lobes and recesses at the segment ends. However, in Fig. 8 the torch is so adjusted or handled as to cut a wider path at one side of the pipe than at the other, when forming the cuts between the lowermost segments. The force exerted by spring 30 then acts to take up the spaces between segments as formed by the torch, and since those spaces are of different widths, the overall result is a bowing of the lower portion of the device, as shown.

The apparatus is lowered into a well in this longitudinally bowed condition and with the lower end 36c engaging the bore wall, and during such lowering is simultaneously rotated, so that the lower end of the apparatus searches for and ultimately finds and advances into the previously drilled drain hole. The apparatus may then be advanced into the drain hole, after which the upper section may be disconnected and removed, leaving the lower section in the hole as a wall supporting structure. During lowering of the apparatus, circulation fluid may be supplied to the lower end of the device through lower hose 29c and an upper communicating hose 1290.

We claim:

1. The method that comprises lowering into the main bore of a well a rotary drilling shaft having a lower tubular longitudinally flexible portion and carrying a drill bit, deflecting said drill bit laterally from the main bore, rotating and advancing the shaft and bit while thus deflected to drill a laterally extending drain hole and to advance said flexible portion of the drill shaft into said hole, disconnecting said lower flexible portion of the drill shaft while in said hole from an upper portion of the shaft, and removing said upper portion of the shaft from the well while leaving said lower flexible portion thereof in said drain hole to support the wall thereof.

2. The method that comprises lowering into the main bore of a well a rotary drilling shaft having a lower tubular longitudinally flexible portion carrying a drill bit at its lower end and containing a flexible circulation hose leading to said bit, deflecting said drill bit laterally from the main bore, rotating and advancing the shaft and bit while thus deflected to drill a laterally extending drain hole and to advance said flexible portion of the drill shaft into said hole, disconnecting said lower flexible portion of the drill shaft while in said hole from an upper portion of the shaft, and removing said upper portion of the shaft and said circulation hose from the well while leaving said lower flexible portion of the shaft in said drain hole to support the wall thereof.

3. The method that comprises lowering into the main bore of a well a rotary drilling shaft having a lower tubular longitudinally flexible portion carrying a drill bit at its lower end and containing a flexible circulation hose leading to said bit, deflecting said drill bit laterally from the main bore, rotating and advancing the shaft and bit while thus deflected to drill a laterally extending drain hole and to advance said flexible portion of the drill shaft into said hole, disconnecting said lower flexible portion ,of the drill shaft while in said hole from an upper portion of the shaft and at substantially the juncture of said main bore and drain hole, disconnecting a lower end of said circulation hose from the bit, and removing said upper portion of the shaft and said circulation hose from the well while leaving said lower flexible portion of the shaft in said drain hole to support the wall thereof.

4. Apparatus comprising an elongated rotary drilling shaft to be lowered into the main bore of a well and including an upper section and a longitudinally flexible lower section adapted to drill and be advanced into .a drain hole extending laterally from the main bore, said lower section including an elongated tubular longitudinally flexible body and a drilling bit carried at the lower end of said body, and a connection between said sections preformed to be broken by force exerted against said upper section to permit removal of the upper section from the well while leaving the lower section in said drain hole to support the wall thereof.

5. Apparatus comprising an elongated unit to be lowered into the main bore of a well and including an upper section and a longitudinally flexible tubular lower section adapted to be advanced into a drain hole extending laterally from the main bore, a flexible circulation hose extending through said sections to deliver fluid to said lower section, a connection between said sections preformed to be broken by force exerted against said upper section to permit removal of the upper section from the well while leaving the lower section in said drain hole to support the wall thereof, and a fluid passing connection between said hose and a lower portion of said lower section at a location spaced beneath said first connection and releasable by force exerted on the hose to permit removal of said hose from the well independently of said lower section.

6. Apparatus comprising an elongated rotary drilling shaft to be lowered into the main bore of a well and including an upper section and a longitudinally flexible tubular lower section adapted to be advanced into a drain hple extending laterally from the main bore, a "bit carried at -thelower end of said'lower section of the shaft for drilling said drain hole, a flexible circulation hose extending downwardly'through said shaft to deliver fluid to the bit, a connection between said sections preformed to be broken by force exerted against said upper section to permit removal of the upper section from the well while leaving the lower section in said drain hole to support the wall thereof, and a fluid passing connection between said hose and bit releasable by force exerted on the hose to permit removal of said hose from the well independently of said lower section of the shaft.

7. Apparatus comprising an elongated rotary drilling shaft tobe lowered into the main bore of a well and including a pair of upper and lower longitudinally flexible sections the lower of which is adapted to be advanced'into a drain hole extending laterally from the main bore, each of said sections comprising a series of articulately interconnected rigid tubular segments, a drill bit carried at the lower end of said lower section of the shaft for drilling said drain ho1e,a flexible circulation hose extending downwardly through said shaft to deliver fluid to the bit, a loose threaded joint between i said sections constructed to be broken by counter-clockwise rotation'of' said upper section to permit removal of the upper section from the well while leaving the lowersection in said drain hole to support the wall thereof, and a sliding telescopic connection between a lower end of said'hose and said bit releasable by a pulling force exerted on the hose to permit removal of said hose from the well independently of said lower section of the shaft. 7 V

8. Apparatus comprising an elongated unit to 'be lowered into the main bore of a well and including an upper section and a longitudinally flexible tubular lower section adapted to be advanced into a drain hole extending laterally from the main bore, a flexible fluid circulation hose extending axially within said unit to the lower end of said lower section, an elongated longitudinally tensioned coil spring extending within said hose and connected at opposite ends to axially spaced portions of :said lower section to yieldingly longitudinally bow 'said lower section andthereby urge its lower end into engagement with the bore wall for reception within said drain hole, and a connection between said sections preformed to be broken byforce exerted against said upper section to permit removal of the upper section from the well while leaving h l r ct n in i drain rect support the wall thereof.

' '9. The method that comprises lowering 'then'iain bore of a well a drill string having a lower flexible portion, drilling with said string a drain hole extendinglaterally from said main bore and advancing the flexible portion of the string during said drilling into said drain hole, disconnecting said lower flexible portion of the drill string while in said hole from anupper portion of the string, and removing said upper portion of the string from the well while leaving said lower flexibleportiona thereof in the drain "hole. I

'10. The method as recited in claim 9, in which said upper portion of the string is disconnected from said lower portion at substantially the juncture of said rnain bore and the drain hole.

of the string.

l2. Apparatus comprising an elongated longitudinally flexible tubularunit to be lowered into the main bore of a well and then advanced into a drain hole extending laterally from said main bore, a spring carried by said tubular unit and yieldingly tending to deflect the lower end of said unit against the bore wall ,to cause said end to engage and move into said drain hole as the unit is lowered, and a fluid circulation hose extending longitudinally within said tubular unit and containing said spring.

13. Apparatus as recited in claim 5, in which said fluid passing connection comprises two tubular elernenis attached tosaid hose and to a lower end portion of said lower section respectively and forming a sliding telescopic essentially fluid tight connection. 7

References Cited in the file of this patent UNITED STATES PATENTS 

